6 - Wikipedia
6 is the largest of the four all-Harshad numbers.. A six-sided polygon is a hexagon, one of the three regular polygons capable of tiling the plane. Figurate numbers representing hexagons (including six) are called hexagonal numbers.Because 6 is the product of a power of 2 (namely 2 1) with nothing but distinct Fermat primes (specifically 3), a regular hexagon is a constructible polygon.